Perl Debugging Using Flags

So my goal is to find an easy way to turn on print statements in Perl using a flag. In C/C++ you can use a #define to choose if certain code is run and it is a way to turn on and off debug print statements. If a #define DEBUG is defined, then you print something, else you run it without the print statements. I was wondering if there was an easy way to do this in Perl.

Here is an example of how it would work:

for($i = 0 ; $i < 10; $i++){
    if(debug flag){
         print some info;
    }
    do operational stuff.
}

Now from the command line you could do one of two things:

1.Run without the debug print statements

perlScript.pl

2.Run with debug print statements

perlScript.pl -debug

Or if someone has a better idea please let me know!

Solution

In perl, compile time is also run time. So there's really not a great deal of advantage in using #define type statements.

My usual trick is:

my $debug = 0; 
$debug += scalar grep ( "-d", @ARGV );

(GetOpt is probably honestly a better plan though)

And then use:

print if $debug;
print $statement if $debug > 2;

Which means I've an easy way of setting the verbosity, and also allowing me to be selective about it by incrementing the statements.

Sometimes I'll embed a signal handler to also adjust debugging level -

#!/usr/bin/perl

use strict;
use warnings;

my $debug = 0; 
$debug += scalar grep ( "-d", @ARGV ); 

$SIG{'USR1'} = { $debug++ };
$SIG{'USR2'} = { $debug-- };

while ( 1 ) {
    print "Debugging at: $debug\n";
    sleep 1;
}

It's more a question of what sort of code I'm writing - this latter I particularly like when doing forky stuff, because then I can adjust debug levels in each fork independently and on the fly.